Wide-range calibration method, measurement method and equipment for eddy current sensor

Abstract

The invention provides a wide-range calibration method, measurement method and equipment for an eddy current sensor, and the calibration method comprises the steps: obtaining a basic value measurement signal and a wafer measurement signal which are obtained through the detection of a sample wafer by the eddy current sensor, calculating the difference between the wafer measurement signal and the basic value measurement signal, and calculating the difference between the wafer measurement signal and the basic value measurement signal; an eddy current signal used for representing eddy current generated by the metal layer on the sample wafer is obtained; superposing the eddy current signal and the plurality of sample base value signals to obtain a plurality of sample wafer signals, and calculating a sample phase difference between the sample base value signals and the corresponding sample wafer signals; selecting a plurality of candidate base value signals from the plurality of sample base value signals according to the sample phase difference and the resolution condition; and overlapping the candidate basic value signal with eddy current signals corresponding to a plurality of wafer thicknesses covering the target range to obtain candidate calibration data, and determining wafer thickness calibration data with a wide range and a calibration basic value signal corresponding to the wafer thickness calibration data from the plurality of candidate calibration data.

Description

Technical Field

[0001] This application relates to the field of wafer polishing technology, and in particular to a large-range calibration method, measurement method and device for eddy current sensors. Background Technology

[0002] In integrated circuit manufacturing, surface treatment of silicon wafers is a crucial step. First, a conductive layer is deposited on the silicon wafer surface. This process requires precise control of deposition conditions to ensure the uniformity and conductivity of the conductive layer meet the requirements of subsequent processes. Then, chemical mechanical polishing (CMP) is used to planarize the surface of the deposited silicon wafer. The CMP process removes surface irregularities through the synergistic effect of chemical etching and mechanical abrasion, achieving a high degree of surface planarization and providing a smooth substrate for subsequent micro / nano fabrication steps.

[0003] In the CMP (Chemical Polishing) process, the endpoint detection system plays a crucial role. This system acquires precise thickness data by monitoring the thickness changes of the thin film on the wafer surface in real time. This data is used not only to determine whether polishing has reached the predetermined endpoint, but also to adjust polishing parameters such as polishing pressure, polishing fluid flow rate, and rotation speed based on real-time feedback, ensuring the stability and uniformity of the polishing process. Through this real-time monitoring and feedback control mechanism, defects and thickness inhomogeneities on the wafer surface can be effectively reduced, thereby improving the overall performance and yield of integrated circuits. Summary of the Invention

[0004] In view of this, this application provides a large-range calibration method, measurement method and device for eddy current sensors to at least partially solve the above problems.

[0005] According to a first aspect of this application, a large-range calibration method for an eddy current sensor is provided, comprising: acquiring a baseline measurement signal and a wafer measurement signal obtained by the eddy current sensor from a sample wafer; calculating the difference between the wafer measurement signal and the baseline measurement signal to obtain an eddy current signal characterizing the eddy current generated on the metal layer of the sample wafer; superimposing the eddy current signal with multiple sample baseline signals to obtain multiple sample wafer signals, and calculating the sample phase difference between the sample baseline signals and the corresponding sample wafer signals, wherein the amplitudes or phases of the multiple sample baseline signals are different; selecting multiple candidate baseline signals from the multiple sample baseline signals according to the sample phase difference and a resolution condition, wherein the resolution condition is that the difference between the sample phase difference and the maximum value of the multiple sample phase differences is less than a preset value; superimposing the candidate baseline signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain candidate calibration data corresponding to the candidate baseline signals, and determining wafer thickness calibration data with a large range and its corresponding calibration baseline signal from the multiple candidate calibration data.

[0006] Preferably, the step of selecting multiple candidate base value signals from multiple sample base value signals based on the sample phase difference and resolution condition includes: determining the maximum value of the sample phase difference from multiple sample phase differences; determining the phase difference range corresponding to the resolution condition based on the maximum value; and determining the sample base value signals whose sample phase differences are within the phase difference range as candidate base value signals.

[0007] Furthermore, the step of superimposing candidate baseline signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain candidate calibration data corresponding to the candidate baseline signals, and determining wafer thickness calibration data with a large range from the multiple candidate calibration data, includes: determining eddy current signals corresponding to multiple wafer thicknesses covering the target range; superimposing multiple eddy current signals with candidate baseline signals to obtain multiple wafer signals corresponding to the candidate baseline signals, and determining candidate calibration data corresponding to the candidate baseline signals based on the multiple wafer signals; calculating the effective range of the candidate calibration data, and determining wafer thickness calibration data with a large range from the candidate calibration data based on the effective range.

[0008] Optionally, the step of superimposing multiple eddy current signals to obtain candidate base value signals, and determining candidate calibration data corresponding to the candidate base value signals based on the multiple wafer signals, includes: superimposing multiple eddy current signals to obtain candidate base value signals, and generating candidate calibration data based on the multiple wafer signals, wherein the candidate calibration data includes the correspondence between wafer thickness and wafer signals. Preferably, the step of calculating the effective range of the candidate calibration data and determining wafer thickness calibration data with a large range based on the effective range includes: calculating the effective range and resolution of the candidate calibration data; and determining wafer thickness calibration data from the candidate calibration data based on the effective range and resolution.

[0009] Furthermore, the candidate calibration data includes the correspondence between wafer thickness and the phase of the wafer signal, and / or the correspondence between wafer thickness and the amplitude of the wafer signal.

[0010] The present invention also provides a thickness measurement method, comprising: determining wafer thickness calibration data with a large range and its corresponding calibration base value signal based on the above method; during the chemical mechanical polishing of the wafer by the chemical mechanical polishing equipment, acquiring the base value signal generated by the signal source of the eddy current sensor, and acquiring the wafer signal collected by the eddy current sensor; calculating the eddy current signal based on the wafer signal and the base value signal, and superimposing the calibration base value signal and the eddy current signal to obtain the corrected wafer signal; determining the wafer thickness based on the corrected wafer signal and the wafer thickness calibration data.

[0011] The present invention also provides a chemical mechanical polishing (CMP) apparatus, comprising: a polishing disc, a support head, a liquid supply device, an eddy current sensor, and a controller; a polishing pad is disposed on one side of the polishing disc; the support head is used to limit the wafer to be polished, so that a metal film disposed on one circular surface of the wafer abuts against the polishing pad and drives the wafer to move relative to the polishing pad, thereby performing CMP on the wafer; the liquid supply device is used to supply polishing liquid to the polishing pad during the CMP process; the eddy current sensor is disposed on the polishing disc and is used to measure the thickness of the wafer; the controller is used to execute the various steps of the above method.

[0012] The present invention also provides a computer storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method.

[0013] The present invention also provides a computer program product, including computer instructions that instruct a computing device to perform the above-described method.

[0014] The beneficial effects of this invention are as follows: by superimposing the eddy current signal with multiple sample base value signals, selecting candidate base value signals based on sample phase difference and resolution conditions, and then superimposing the candidate base value signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range, wafer thickness calibration data with a large range is finally determined, realizing dynamic real-time large-range signal measurement with a real-time dynamic measurement accuracy of less than 10nm; improving the range of real-time eddy current measurement without changing the measurement accuracy (static measurement accuracy 0.2nm); improving the resolution capability of the original accuracy signal through compensation and correction based on the original signal, greatly improving the measurement performance; avoiding the jump problem caused by frequency switching, and achieving accurate measurement of a larger range of thicknesses at a fixed frequency. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0016] Figure 1 This is a schematic diagram of a chemical mechanical polishing apparatus according to an embodiment of this application;

[0017] Figure 2 It is an eddy current phase signal map obtained by detecting the film thickness of various Cu at a fixed frequency;

[0018] Figure 3 It is a signal graph of eddy current amplitude obtained by detecting the film thickness of various Cu at a fixed frequency;

[0019] Figure 4 This is a flowchart of a large-range calibration method for an eddy current sensor according to an embodiment of this application;

[0020] Figure 5 This is a phase diagram of a calculated eddy current signal according to one embodiment of this application;

[0021] Figure 6 This is a schematic diagram of a plurality of sample base value signals superimposed with an eddy current signal according to an embodiment of this application;

[0022] Figure 7 This is a schematic diagram of candidate calibration data corresponding to multiple candidate base value signals according to an embodiment of this application;

[0023] Figure 8 This is a flowchart of a thickness measurement method according to an embodiment of this application. Detailed Implementation

[0024] This application provides a large-range calibration method for eddy current sensors. This method can be applied to controllers or processors in chemical mechanical polishing equipment, or to controllers or processors included in a test bench. The test bench is a relatively simple test bench built according to the working principle of chemical mechanical polishing equipment. This application does not limit it. Through this method, eddy current sensors can be calibrated during the chemical mechanical polishing process of wafers in chemical mechanical polishing equipment or test bench.

[0025] Figure 1 This is a schematic diagram of a chemical mechanical polishing apparatus according to an embodiment of this application. Figure 1 As shown, the chemical mechanical polishing (CMP) equipment is used to perform CMP on wafers, specifically on a thin metal film on a circular surface of the wafer. The metal film is the object to be polished. The CMP equipment includes: a polishing disc 1, a support head 2, a liquid supply device, an eddy current sensor 3, and a controller. A circular polishing pad 11 is provided on one side of the polishing disc 1. The polishing disc 1 is used to drive the polishing pad 11 to rotate around its axis. The support head 2 is used to limit the wafer to be polished so that the metal film abuts against the polishing pad 11 during CMP. Specifically, the metal film on the wafer abuts against the side of the polishing pad 11 away from the polishing disc 1. Furthermore, the support head 2 is also used to drive the wafer around its axis. The wafer rotates and reciprocates along the radial direction of the polishing pad 11 on the side of the polishing pad 11 away from the polishing disk 1, thereby achieving chemical mechanical polishing of the wafer; the liquid supply device is used to supply polishing liquid to the polishing pad 11 during the chemical mechanical polishing of the wafer; the eddy current sensor 3 is disposed on the polishing disk 1, so that the eddy current sensor 3 and the wafer are respectively located on both sides of the polishing pad 11, and the eddy current sensor 3 is also driven by the polishing disk 1 to rotate around the axis of the polishing pad 11 during the rotation of the polishing pad 11 driven by the polishing disk 1, the eddy current sensor 3 is used to measure the thickness of the wafer, specifically the thickness of the metal thin film disposed on the wafer; the controller is used to execute the calibration method for the eddy current sensor 3.

[0026] Based on the aforementioned chemical mechanical polishing equipment or test bench (hereinafter collectively referred to as calibration equipment), the following describes in detail the large-range calibration method for eddy current sensors through multiple embodiments.

[0027] In integrated circuit manufacturing, global planarization of the conductive layer on the silicon wafer surface relies on chemical mechanical polishing (CMP). This process requires an endpoint detection system to dynamically monitor the film thickness on the wafer surface in real time and accurately determine the polishing endpoint or dynamically adjust process parameters (such as pressure and rotation speed) based on the measurement results. However, eddy current detection technology faces significant challenges in practical applications: due to the skin effect, the linear correspondence between the metal film thickness and the sensor response signal exists only within a limited detection range. Taking copper interconnect layer polishing as an example, its initial thickness is often in the micrometer range (1-3 μm), while the target thickness at the endpoint needs to reach nanometer-level precision (<100 nm). Therefore, the detection system needs to operate within a dynamic range spanning three orders of magnitude (10... -9 ~10 -6 Simultaneously achieving high sensitivity and high signal-to-noise ratio places stringent demands on sensor design and signal analysis algorithms.

[0028] Specifically, see Figure 2 The figure shows the eddy current phase signal obtained by detecting the thickness of various Cu films at a fixed frequency. The horizontal axis corresponds to the phase signal value, and the vertical axis corresponds to the film thickness. Figure 2 As shown, it has a signal reflection region A, meaning that the same phase signal corresponds to two thicknesses; see [link / reference]. Figure 3 The figure shows the eddy current amplitude signal obtained by detecting Cu at a fixed frequency. The horizontal axis corresponds to the amplitude signal value, and the vertical axis corresponds to the film thickness. Figure 3 As shown, there is a region B where the measurement accuracy is insufficient.

[0029] One possible measurement approach is to extend the dynamic range of eddy current detection by optimizing the frequency parameters of the excitation signal: high-frequency excitation (>10MHz) can improve the resolution of nanoscale thin films, while low-frequency excitation (<1MHz) is suitable for stable measurement of micrometer-scale thicknesses. Based on this, a segmented frequency switching model was studied to cover the entire thickness range. However, actual tests show that the frequency switching process causes nonlinear jumps in the sensor output signal (typical error >5%), severely affecting the continuity of cross-scale thickness measurement. Especially for monitoring scenarios where film thickness continuously decays during copper wiring polishing, the jumps caused by frequency switching can introduce false endpoint signals or trigger misjudgments. Therefore, how to overcome the skin depth limitation at a single fixed frequency and achieve seamless continuous detection from micrometers to nanometers is one of the core research directions for improving the control accuracy of CMP processes.

[0030] See Figure 4 Based on this, this application provides a large-range calibration method for eddy current sensors, including:

[0031] S101. Obtain the baseline measurement signal and the wafer measurement signal obtained by the eddy current sensor from the sample wafer, calculate the difference between the wafer measurement signal and the baseline measurement signal, and obtain the eddy current signal used to characterize the eddy current generated on the metal layer of the sample wafer.

[0032] In this embodiment, after the eddy current sensor included in the calibration equipment is powered on, and before the calibration equipment performs chemical mechanical polishing on the wafer, the excitation signal generated by the signal source included in the eddy current sensor at any time is acquired.

[0033] For example, before the calibration equipment performs chemical mechanical polishing on the wafer, the eddy current sensor is first powered on. After a period of time, the signal generated by the signal source of the eddy current sensor is acquired as the excitation signal. The signal generated by the signal source of the eddy current sensor is the source signal that causes the coil of the eddy current sensor to generate an alternating electromagnetic field.

[0034] When there is no wafer above the eddy current sensor, the signal detected by the eddy current sensor is the baseline measurement signal. When there is a wafer above the eddy current sensor, the detected signal is the wafer measurement signal. Therefore, by calculating the difference between the baseline measurement signal and the wafer measurement signal, the eddy current signal that characterizes the eddy current generated by the metal layer on the sample wafer can be obtained.

[0035] For ease of understanding, see Figure 5 The diagram illustrates an exemplary phase diagram for calculating eddy current signals. The wafer measurement signal and the baseline measurement signal are represented by vectors. The length of the vector is the signal amplitude, and the angle between the vector and the positive x-axis is the signal phase. Calculating the difference between the baseline measurement signal and the wafer measurement signal can be understood as subtracting the vector β corresponding to the wafer measurement signal from the vector α corresponding to the baseline measurement signal. The resulting vector γ is the vector corresponding to the eddy current signal.

[0036] S102. The eddy current signal is superimposed with multiple sample base value signals to obtain multiple sample wafer signals, and the sample phase difference between the sample base value signals and the corresponding sample wafer signals is calculated.

[0037] The amplitudes or phases of multiple sample base signals are different.

[0038] Still with Figure 5 For example, superimposing the eddy current signal with multiple sample base value signals can be achieved by superimposing the vector γ corresponding to the eddy current signal onto the vector δ (dashed line) corresponding to the sample base value signal, thus obtaining the vector ε (dashed line) corresponding to the sample wafer signal.

[0039] A schematic diagram showing the superposition of multiple sample base signals with an eddy current signal can be shown as follows: Figure 6 As shown, Figure 6The short lines in the diagram represent eddy current signals. The vector pointing from the origin to the starting point of the eddy current signal represents the sample base signal, and the vector pointing from the origin to the ending point of the eddy current signal represents the sample wafer signal.

[0040] In this embodiment, to obtain a large range of calibration data, it is necessary to select a suitable base value signal. Therefore, multiple different sample base value signals are generated, with different amplitudes or phases. For example, multiple sample base value signals with amplitudes ranging from 0.5V to 5V and phases varying from 0° to 360° can be generated.

[0041] For each sample baseline signal, it is superimposed with the previously acquired eddy current signal to obtain the corresponding sample wafer signal. Then, the phase difference between each sample baseline signal and the corresponding sample wafer signal is calculated, i.e., the sample phase difference. The sample phase difference is an important indicator for evaluating the applicability of the baseline signal. It reflects the phase relationship between the baseline signal and the wafer signal and has a significant impact on the accuracy of subsequent thickness measurements.

[0042] S103. Based on the sample phase difference and resolution condition, select multiple candidate base value signals from multiple sample base value signals, wherein the resolution condition is that the difference between the sample phase difference and the maximum value of the multiple sample phase differences is less than a preset value.

[0043] In this embodiment, the maximum value of the sample phase difference is determined from multiple sample phase differences. For example, assuming the calculated sample phase difference range is 10°-35°, the maximum value is 35°.

[0044] The phase difference range corresponding to the resolution condition is determined based on the maximum value. In this embodiment, the preset value is set to 20% of the maximum value, i.e., 35° × 20% = 7°. Therefore, the resolution condition is: the difference between the sample phase difference and the maximum value is less than 7°, i.e., the phase difference range is 28° to 35°.

[0045] Based on the resolution conditions described above, candidate base value signals that meet the conditions are selected from multiple sample base value signals. In this example, sample base value signals corresponding to sample phase differences within the range of 28° to 35° can be selected as candidate base value signals.

[0046] To facilitate subsequent calculations, instead of determining a single sample base value signal as a candidate base value signal, the above judgment method can be used. Instead, the phase difference of the sample base value signal whose amplitude is in the range of ([base_amp]_t1-[base_amp]_t2) and whose phase is in the range of ([base_phi]_t1-[base_phi]_t2) meets the resolution condition, and the sample base value signal in this range is determined as the candidate base value signal.

[0047] S104. Superimpose the candidate base value signal with the eddy current signal corresponding to multiple wafer thicknesses covering the target range to obtain the candidate calibration data corresponding to the candidate base value signal, and determine the wafer thickness calibration data with a large range and its corresponding calibration base value signal from the multiple candidate calibration data.

[0048] In this embodiment, eddy current signals corresponding to multiple wafer thicknesses covering the target measurement range are first determined. The target measurement range refers to the range of wafer thicknesses to be measured, for example, from 100nm to 1000nm. Within this range, multiple thickness points are selected, such as 100nm, 200nm, 300nm...1000nm, and eddy current signals corresponding to these thicknesses are acquired or simulated.

[0049] These eddy current signals are superimposed on each candidate baseline signal to obtain multiple wafer signals corresponding to each candidate baseline signal. Based on these wafer signals, candidate calibration data is generated, which includes the correspondence between wafer thickness and wafer signals. This correspondence can be between the phase of the wafer thickness and the phase of the wafer signal, or between the amplitude of the wafer thickness and the wafer signal, or both.

[0050] Candidate calibration data corresponding to multiple candidate base signals can be as follows Figure 7 As shown, Figure 7 The vertical axis represents the wafer thickness, and the horizontal axis represents the phase signal of the wafer signal. Figure 7 One curve in the graph corresponds to one candidate base value signal.

[0051] Calculate the effective range and resolution for each candidate calibration data point. The effective range refers to the range of wafer thickness that can be accurately measured under the given candidate baseline signal; the resolution refers to the smallest thickness difference that can be distinguished within that range. Specifically, this can be calculated... Figure 7 The slope of each point on the curve is approximately equal to the x-axis. The higher the resolution, the larger the range of the curve's ordinate and the larger the effective range when the resolution is sufficient.

[0052] Based on the effective measurement range and resolution, the optimal wafer thickness calibration data and its corresponding calibration baseline signal are determined from the candidate calibration data. Typically, the candidate calibration data with the largest effective measurement range and satisfactory resolution is selected as the final wafer thickness calibration data.

[0053] The wafer thickness calibration data not only stores the correspondence between wafer thickness and wafer signal, but also includes its corresponding calibration base value signal.

[0054] The proposed solution superimposes eddy current signals with multiple sample baseline signals, selects candidate baseline signals based on sample phase difference and resolution conditions, and then superimposes these candidate baseline signals to cover multiple wafer thicknesses within the target measurement range. This process ultimately determines wafer thickness calibration data with a large measurement range, achieving dynamic real-time measurement of signals with a large range. The real-time dynamic measurement accuracy is less than 10 nm. The solution improves the real-time measurement range of eddy currents without altering the measurement accuracy (static measurement accuracy is 0.2 nm). Compensation and correction based on the original signal enhance the resolution of the original accuracy signal, significantly improving measurement performance. It avoids the jump problem caused by frequency switching, enabling accurate measurement of a larger thickness range at a fixed frequency. Experiments show that when measuring the thickness of copper (Cu) using the corrected method, the measurement error is less than 10 nm within the thickness range of 5000 nm to 20 nm, greatly improving the measurement range.

[0055] It should also be noted that the above methods can be performed by a chemical mechanical polishing machine or by a test platform, both of which are within the scope of protection of this application.

[0056] This application provides a thickness measurement method. Figure 8 This is a flowchart of a thickness measurement method according to an embodiment of this application.

[0057] like Figure 8 As shown, the thickness measurement method includes the following steps:

[0058] S201. Determine the wafer thickness calibration data with a large range and its corresponding calibration base value signal.

[0059] For the specific determination method, please refer to the above embodiments, which will not be repeated here.

[0060] S202. During the chemical mechanical polishing process of the wafer in the chemical mechanical polishing equipment, the base value signal generated by the signal source of the eddy current sensor is acquired, and the wafer signal collected by the eddy current sensor is acquired.

[0061] During chemical mechanical polishing (CMP), the eddy current sensor's signal source generates a baseline signal, while the eddy current sensor simultaneously acquires a wafer signal. These two signals are acquired in real time and used for subsequent thickness calculations.

[0062] S203. Calculate the eddy current signal based on the wafer signal and the base signal, and superimpose the calibration base signal and the eddy current signal to obtain the corrected wafer signal.

[0063] The difference between the wafer signal and the baseline signal is calculated to obtain the eddy current signal. Then, the calibration baseline signal determined in Example 1 is superimposed with the eddy current signal to obtain the corrected wafer signal. The purpose of this step is to convert the signal under actual measurement conditions into a signal consistent with the calibration conditions so that the calibration data can be used for thickness calculation.

[0064] S204. Determine the wafer thickness based on the corrected wafer signal and wafer thickness calibration data.

[0065] The thickness of the current wafer is determined using the corrected wafer signal and the wafer thickness calibration data obtained in Example 1. Specifically, the wafer thickness value can be obtained by finding the data point in the calibration data that is closest to the corrected wafer signal, or by interpolation.

[0066] The above method allows for real-time and accurate measurement of wafer thickness during chemical mechanical polishing, providing important data for process control.

[0067] It should be noted that the thickness measurement method in this embodiment is based on the aforementioned large-range calibration method for eddy current sensors, and therefore has the same beneficial effects as the embodiment of the large-range calibration method for eddy current sensors, which will not be repeated here.

[0068] Corresponding to the above-described embodiments of the large-range calibration method for eddy current sensors, this application discloses a chemical mechanical polishing apparatus, such as... Figure 1 As shown, the chemical mechanical polishing equipment includes: a polishing disc 1, a bearing head 2, a liquid supply device, an eddy current sensor 3, and a controller;

[0069] A polishing pad 11 is provided on one side of the polishing disc 1;

[0070] The carrier head 2 is used to limit the wafer to be polished so that the metal film on one circular surface of the wafer abuts against the polishing pad 11 and drives the wafer to move relative to the polishing pad 11 to perform chemical mechanical polishing on the wafer.

[0071] A liquid supply device is used to supply polishing liquid to the polishing pad 11 during the chemical mechanical polishing of the wafer.

[0072] Eddy current sensor 3 is mounted on polishing disk 1 and is used to measure the thickness of the wafer;

[0073] The controller is used to perform the following processes:

[0074] The process involves acquiring a baseline measurement signal and a wafer measurement signal obtained from an eddy current sensor detecting a sample wafer, calculating the difference between the wafer measurement signal and the baseline measurement signal to obtain an eddy current signal characterizing the eddy currents generated on the metal layer of the sample wafer, superimposing the eddy current signal with multiple sample baseline signals to obtain multiple sample wafer signals, and calculating the sample phase difference between the sample baseline signals and the corresponding sample wafer signals, wherein the amplitudes or phases of the multiple sample baseline signals are different; selecting multiple candidate baseline signals from the multiple sample baseline signals based on the sample phase difference and a resolution condition, wherein the resolution condition is that the difference between the sample phase difference and the maximum value of the multiple sample phase differences is less than a preset value; superimposing the candidate baseline signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain candidate calibration data corresponding to the candidate baseline signal, and determining wafer thickness calibration data with a large range and its corresponding calibration baseline signal from the multiple candidate calibration data.

[0075] Optionally, selecting multiple candidate base value signals from multiple sample base value signals based on the sample phase difference and resolution condition includes: determining the maximum value of the sample phase difference from multiple sample phase differences; determining the phase difference range corresponding to the resolution condition based on the maximum value; and determining the sample base value signals whose sample phase differences are within the phase difference range as candidate base value signals.

[0076] Optionally, the step of superimposing candidate baseline signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain candidate calibration data corresponding to the candidate baseline signals, and determining wafer thickness calibration data with a large range from the multiple candidate calibration data, includes: determining eddy current signals corresponding to multiple wafer thicknesses covering the target range; superimposing multiple eddy current signals onto the candidate baseline signal to obtain multiple wafer signals corresponding to the candidate baseline signal, and determining candidate calibration data corresponding to the candidate baseline signal based on the multiple wafer signals; calculating the effective range of the candidate calibration data, and determining wafer thickness calibration data with a large range from the candidate calibration data based on the effective range.

[0077] Optionally, the step of superimposing multiple eddy current signals onto a candidate base value signal to obtain multiple wafer signals corresponding to the candidate base value signal, and determining candidate calibration data corresponding to the candidate base value signal based on the multiple wafer signals, includes: superimposing multiple eddy current signals onto a candidate base value signal to obtain multiple wafer signals corresponding to the candidate base value signal; generating candidate calibration data based on the multiple wafer signals, wherein the candidate calibration data includes the correspondence between wafer thickness and wafer signal.

[0078] Optionally, the step of calculating the effective range of the candidate calibration data and determining the wafer thickness calibration data with a large range from the candidate calibration data based on the effective range includes: calculating the effective range and resolution of the candidate calibration data; and determining the wafer thickness calibration data from the candidate calibration data based on the effective range and resolution.

[0079] Optionally, the candidate calibration data includes the correspondence between wafer thickness and the phase of the wafer signal, and / or the correspondence between wafer thickness and the amplitude of the wafer signal.

[0080] Alternatively, the processor can also be used to perform the following processes:

[0081] Determine wafer thickness calibration data with a large range and its corresponding calibration base value signal; during the chemical mechanical polishing of the wafer in the chemical mechanical polishing equipment, acquire the base value signal generated by the signal source of the eddy current sensor, and acquire the wafer signal collected by the eddy current sensor; calculate the eddy current signal based on the wafer signal and the base value signal, and superimpose the calibration base value signal and the eddy current signal to obtain the corrected wafer signal; determine the wafer thickness based on the corrected wafer signal and the wafer thickness calibration data.

[0082] In one specific embodiment, the chemical mechanical polishing equipment can be the chemical mechanical polishing equipment described in the above embodiments of the calibration method for eddy current sensors, and the controller is used to execute the above-described large-range calibration method or thickness measurement method for eddy current sensors.

[0083] It should be noted that the controller included in the chemical mechanical polishing equipment of this embodiment is used to implement the large-range calibration method or thickness measurement method for the eddy current sensor in the foregoing method embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0084] In this embodiment, a computer-readable storage medium is provided, storing instructions for causing a machine to perform a large-range calibration method or thickness measurement method for an eddy current sensor, as described herein. Specifically, a system or apparatus equipped with a storage medium storing software program code that implements the functions of any of the embodiments described above, and enabling the computer (or CPU or MPU) of the system or apparatus to read and execute the program code stored in the storage medium.

[0085] In this case, the program code read from the storage medium can itself implement the functions described in the above method embodiments, so the program code and the storage medium storing the program code constitute a part of this application.

[0086] Examples of storage media used to provide program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer via a communication network.

[0087] In this embodiment, a computer program product is provided, including computer instructions that instruct a computing device to perform the operations corresponding to the above-described method embodiments.

[0088] It should be noted that, depending on the implementation needs, the various components / steps described in this application can be broken down into more components / steps, or two or more components / steps or parts of the operation of a component / step can be combined into a new component / step to achieve the purpose of this application.

[0089] The methods described above according to this application can be implemented in hardware, firmware, or as software or computer code that can be stored in a recording medium (such as a CD-ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code originally stored on a remote recording medium or a non-transitory machine-readable medium and to be stored on a local recording medium, downloaded via a network. Thus, the methods described herein can be processed by software stored on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components (e.g., RAM, ROM, flash memory, etc.) capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods described herein. Furthermore, when a general-purpose computer accesses code used to implement the methods shown herein, the execution of the code transforms the general-purpose computer into a dedicated computer for performing the methods shown herein. Although this application has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art based on a reading and understanding of this specification and the accompanying drawings. This application includes all such modifications and variations and is limited only by the scope of the appended claims.

[0090] That is, the above description is only an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made using the content of this application’s specification and drawings, such as the combination of technical features between different embodiments, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of this application.

[0091] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0092] The above description is provided to enable any person skilled in the art to implement and use this application. Various details are set forth in the above description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be implemented without using these specific details. In other embodiments, well-known processes will not be described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed herein.

[0093] It should be noted that, without conflict, the various embodiments and / or technical features described in this application can be arbitrarily combined with each other, and the resulting technical solutions should also fall within the protection scope of this application.

[0094] It should be understood that the specific examples in this application are only intended to help those skilled in the art better understand this application, and are not intended to limit the scope of this application. Those skilled in the art can make various improvements and modifications based on the above embodiments, and all such improvements or modifications fall within the protection scope of this application.

[0095] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A large-range calibration method for an eddy current sensor, characterized in that, include: The baseline measurement signal and the wafer measurement signal obtained by the eddy current sensor are acquired. The difference between the wafer measurement signal and the baseline measurement signal is calculated to obtain the eddy current signal used to characterize the eddy current generated on the metal layer of the sample wafer. The eddy current signal is superimposed with multiple sample base signals to obtain multiple sample wafer signals, and the sample phase difference between the sample base signals and the corresponding sample wafer signals is calculated, wherein the amplitude or phase of the multiple sample base signals is different. Based on the sample phase difference and resolution condition, multiple candidate base value signals are selected from multiple sample base value signals, wherein the resolution condition is that the difference between the sample phase difference and the maximum value of the multiple sample phase differences is less than a preset value; The candidate baseline signal is superimposed with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain the candidate calibration data corresponding to the candidate baseline signal. The wafer thickness calibration data with a large range and its corresponding calibration baseline signal are determined from the multiple candidate calibration data.

2. The method according to claim 1, characterized in that, The step of selecting multiple candidate base value signals from multiple sample base value signals based on the sample phase difference and resolution conditions includes: The maximum value of the sample phase difference is determined from multiple sample phase differences; The phase difference range corresponding to the resolution condition is determined based on the maximum value, and the sample base value signals whose sample phase difference is within the phase difference range are determined as candidate base value signals.

3. The method according to claim 1, characterized in that, The process of superimposing candidate baseline signals with eddy current signals corresponding to multiple wafer thicknesses covering the target range to obtain candidate calibration data corresponding to the candidate baseline signals, and determining wafer thickness calibration data with a large range from multiple candidate calibration data, includes: The eddy current signals corresponding to multiple wafer thicknesses covering the target range were determined; Multiple eddy current signals are superimposed on the candidate base value signal to obtain multiple wafer signals corresponding to the candidate base value signal, and the candidate calibration data corresponding to the candidate base value signal is determined based on the multiple wafer signals. Calculate the effective range of the candidate calibration data, and determine the wafer thickness calibration data with a large range from the candidate calibration data based on the effective range.

4. The method according to claim 3, characterized in that, The step of superimposing multiple eddy current signals onto a candidate base value signal to obtain multiple wafer signals corresponding to the candidate base value signal, and determining the candidate calibration data corresponding to the candidate base value signal based on the multiple wafer signals, includes: Multiple eddy current signals are superimposed on a candidate base value signal to obtain multiple wafer signals corresponding to the candidate base value signal; Based on multiple wafer signals, candidate calibration data is generated, which includes the correspondence between wafer thickness and wafer signal.

5. The method according to claim 4, characterized in that, The calculation of the effective range of the candidate calibration data, and the determination of a large range of wafer thickness calibration data from the candidate calibration data based on the effective range, includes: Calculate the effective range and resolution of the candidate calibration data; The wafer thickness calibration data is determined from the candidate calibration data based on the effective range and resolution.

6. The method according to claim 4, characterized in that, The candidate calibration data includes the correspondence between wafer thickness and the phase of the wafer signal, and / or the correspondence between wafer thickness and the amplitude of the wafer signal.

7. A thickness measurement method, characterized in that, include: Based on the method described in any one of claims 1-6, wafer thickness calibration data with a large range and its corresponding calibration base signal are determined; During the chemical mechanical polishing process of the wafer in the chemical mechanical polishing equipment, the base value signal generated by the signal source of the eddy current sensor is acquired, and the wafer signal collected by the eddy current sensor is also acquired. The eddy current signal is calculated based on the wafer signal and the baseline signal, and the calibration baseline signal is superimposed with the eddy current signal to obtain the corrected wafer signal. The wafer thickness is determined based on the corrected wafer signal and wafer thickness calibration data.

8. A chemical mechanical polishing apparatus, characterized in that, include: Polishing disc, bearing head, liquid supply device, eddy current sensor and controller; A polishing pad is provided on one side of the polishing disc; The bearing head is used to limit the wafer to be polished so that the metal film on one circular surface of the wafer abuts against the polishing pad and drives the wafer to move relative to the polishing pad to perform chemical mechanical polishing on the wafer. The liquid supply device is used to supply polishing liquid to the polishing pad during the chemical mechanical polishing of the wafer. The eddy current sensor is mounted on the polishing disk and is used to measure the thickness of the wafer. The controller is used to perform the method according to any one of claims 1-7.

9. A computer storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the method as described in any one of claims 1-7.

10. A computer program product, characterized in that, Includes computer instructions that instruct a computing device to perform the method as described in any one of claims 1-7.

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